Despite widespread recognition of the increasing prevalence and medical sequelae of obesity, efforts to reverse these trends have met with limited success. Although 75 percent of obese individuals who enter a weight loss program are initially successful, more than 90 percent of these individuals regain the lost weight within 5 years, leading to renewal or even exacerbation of cardiopulmonary and vascular disease risks. The focus of this proposal is the prevention of weight regain in obese individuals after successful weight loss. The best predictor of weight loss maintenance is the duration and intensity of patient-provider contact, irrespective of practitioner specialty or the nature of the intervention. However, the high costs of intensive interventions over an extended period limit optimal management to a small number of patients. The hypothesis underlying the proposed study is that some of the benefits of intensive patient-provider interaction can be achieved in a cost-efficient manner through creative use of electronic communication. We propose to develop a three-part, web-based program ("WeightConnection") that includes mechanisms for (1) ongoing, patient self-monitoring and graphical feedback about weight, eating and exercise behavior, (2) individual, electronic consultative advice from a weight counselor and (3) on-line group-based therapy and peer-to-peer communication. Our goals for this intervention are to achieve several benefits of intensive patient-provider interaction that appear to underlie successful weight loss maintenance, including sustained patient motivation, diminished attrition rates, and timely relapse management. Each component of the proposed program is designed to promote these goals by providing personal guidance, educational opportunities and psychological support. We will initially test and refine the WeightConnection program with a small group of patient volunteers recruited from MGH Weight Center patients. Thereafter, we will examine whether this intervention improves the success of a standard group-based program in maintaining weight loss. We will conduct a randomized, controlled study in 30-40 patients, comparing the combination of the WeightConnection program and standard therapy vs. standard therapy alone. The results of this pilot study, including effects on weight maintenance and patient retention, preliminary subgroup analysis and careful assessment of patient usage and feedback, will be used to design a more definitive study of the efficacy and cost-effectiveness of electronic communication for prevention of recurrent weight gain.